Saab 340B, Руководство по эксплуатации

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LANDING GEAR
Description
Aircraft Operations Manual
13.1
PAGE 3
Apr 01/15
brake pressure is reduced for both inboard brakes
since they are connected to the same circuit. Simi-
larly, a skid on an outboard wheel will reduce brake
pressure to both outboard brakes. There is also a
locked wheel protection which dumps the brake
pressure in a brake circuit should the wheel speeds
in the circuit differ by more than 50%.
When aircraft speed has decreased to about 20 kts
the anti
− skid system cuts out and braking must
then be modulated manually.
The anti − skid control box circuits and the wheel
speed transducers are continuously monitored for
proper functioning. If any parameter exceeds its
established limits, the A
− SKID INOP light on the
central warning panel comes on.
The light also comes on if the anti − skid switch is
OFF when the gear is extended before landing.
This alerts the pilot to an incorrect switch position.
Emergency braking
Emergency braking must be used if the hydraulic
pump is inoperative. Hydraulic pressure is then
available only from the brake accumulators or from
the hand pump.
The same controls are used for emergency brake
application as for normal braking. The anti
− skid
function is maintained since accumulator capacity is
sufficient for more than one complete landing se-
quence.
Parking brake
The parking brake is controlled by a handle on the
left pilot’ s side panel. By pulling the handle and
then depressing the brake pedals, hydraulic pres-
sure is trapped in the system by means of a parking
brake valve closing the return line when the trapped
pressure exceeds the brake valve set pressure of
1500 psi. The brake valve will remain closed and
the handle remains in pulled (up) position as long
as the trapped pressure exceeds 950 psi. If pres-
sure decreases below 950 psi the valve will auto-
matically open and relieve remaining pressure to
the return line. The handle remains in the pulled
(up) position.The brake handle can be locked in the
pulled position by turning the handle approximately
30

clockwise.
A PARK BRK ON (CWP) light comes on when ap-
plying the parking brake and the trapped pressure
exceeds 1700 psi. Once illuminated, the light will
stay on as long as the trapped pressure remains
above 900 psi.
There is a possibility to set the brakes (handle is
up) without the CWP light coming on if the pres-
sure is just high enough to close the valve (1500
psi) but below the CWP light
− on triggering pres-
sure (1700 psi). Therefore, check CWP light
coming on when parking brake is set.
NOTE
The parking brake is disengaged by turning the
handle approximately 30

counter − clockwise and
pushing down.
2.3 Nose wheel steering (Fig. 3)
Nose wheel steering is hydraulic and operated by a
single hydraulic actuator. The steering system is
operative on ground only and is controlled by a
wheel on the left pilot’ s side panel. Maximum steer-
ing deflection is 60

left or right.
To steer, the wheel must first be pushed down to
engage mechanically with the steering system and
to complete the electrical circuit to open the steer-
ing shutoff valve.
When towing, maximum deflection is 120

or 90

,
depending on mod status, as indicated on the nose
gear. A ground handling lockout switch in the nose-
wheel well is used to deactivate the steering system
during towing.
If the nosewheel is deflected more than 20
 
5

without the steering wheel being pushed down or
ground handling lockout switch is closed, a solenoid
steering brake will lock the wheel in its present posi-
tion, and engage the nose wheel steering system
preventing further deflection.
In flight the nosewheel is automatically centered by
cams in the shock strut.
2.4 Landing Gear switches/relays
There are two air/ground (WOW) switches located
on each main gear and one downlock and one
uplock switch on each gear. These switches are